Rivet analyses

Lepton momentum spectrum in B → X_uℓν decays

Experiment: BABAR (PEP-II)

Inspire ID: 1079912

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 86 (2012) 032004

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+, B0 mesons, originally Upsilon(4S) decay

Measurement of the branching ratio for BX̄ → X_uℓν̄_ℓ for different lower cuts on the lepton momentum.

Source code:`BABAR_2012_I1079912.cc`

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief B -> X_u ell nu
  class BABAR_2012_I1079912 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2012_I1079912);


    /// @name Analysis methods
    /// @{

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(UnstableParticles(Cuts::abspid==511 or
                Cuts::abspid==521),"UFS");
      // histograms
      book(_h,1,1,1);
      book(_nB,"/TMP/nB");
    }

    void findDecayProducts(Particle parent, Particles & em, Particles & ep,
               Particles & nue, Particles & nueBar, bool & charm) {
      for(const Particle & p : parent.children()) {
    if(PID::isCharmHadron(p.pid())) {
      charm=true;
    }
    else if(p.pid() == PID::EMINUS) {
      em.push_back(p);
    }
    else if(p.pid() == PID::EPLUS) {
      ep.push_back(p);
    }
    else if(p.pid() == PID::NU_E || p.pid()==PID::NU_MU) {
      nue.push_back(p);
    }
    else if(p.pid() == PID::NU_EBAR || p.pid()==PID::NU_MUBAR) {
      nueBar.push_back(p);
    }
    else if(PID::isBottomHadron(p.pid())) {
      findDecayProducts(p,em,ep,nue,nueBar,charm);
    }
    else if(!PID::isHadron(p.pid())) {
      findDecayProducts(p,em,ep,nue,nueBar,charm);
    }
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      if(_edges.empty()) _edges=_h->xEdges();
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      for(const Particle& p : ufs.particles()) {
    if(p.children().empty()) continue;
    if(p.children()[0].abspid()==p.abspid()) continue;
    _nB->fill();
    bool charm = false;
    Particles em,ep,nue,nueBar;
    findDecayProducts(p,em,ep,nue,nueBar,charm);
    if(charm) continue;
    FourMomentum pl,pnu;
    if(em.size()==1 && nueBar.size()==1) {
      pl  = em[0].momentum();
    }
    else if(ep.size()==1 && nue.size()==1) {
      pl  = ep[0].momentum();
    }
    else
      continue;
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
    pl  = boost.transform(pl );
    double pp = pl.p3().mod();
        double Emin=1.0;
        for(unsigned int ix=0;ix<_edges.size();++ix) {
      if(pp>Emin) _h->fill(_edges[ix]);
          Emin+=0.1;
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      // 1e3 due br normalization and 0.1 to remove bin width
      scale(_h, 1e3/ *_nB);
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _h;
    CounterPtr _nB;
    vector<string> _edges;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2012_I1079912);

}

Rivet analyses

Lepton momentum spectrum in B → Xuℓν decays

Source code:BABAR_2012_I1079912.cc

Lepton momentum spectrum in B → X_uℓν decays

Source code:`BABAR_2012_I1079912.cc`